Perhaps you should try some spelling variations:
doanh khoa » toan khoa
doc doanh » doi doanh, dong doanh, hoa doanh
sach hoc » cach hoc, sach hoi, mach hoc
cuu nang » chuc nang, cam nang, cuu van
nang doc » nang luc
khoa hoc » hoa hoc
nhan dan » phan dau, nhan tai
gian dan » gian lang
tu sach » thu sach, su sach, te sach
hoa va » hoa van, hoa xa, hoa vo

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach hoc tap, nghien cuu nang doc doanh khoa hoc ma hoa va ((nhan dan) or (gian dan))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach hoc tap, nghien cuu nang doc doanh khoa hoc ma hoa va ((nhan dan) OR (gian dan)).
• Adding a wildcard symbol may retrieve word variants: tu sach hoc tap, nghien cuu nang doc doanh khoa hoc ma hoa va ((nhan dan) or (gian dan))*.